Thursday, April 30, 2009

sparkfun prototype demo

It works (kind of)!My prototype board that plugs into the sparkfun fpga breakout seems to be working to some degree. I can play super mario world, but other games won't boot, even ones that otherwise work in my de2 prototype (same sd card and everything).

How do you get past the problem where the FPGA has to come up before the SNES? Do you give power to the FPGA board so that the FPGA can configure, then do you power the SNES up after configuration? Or, is there enough time for configuration while the SNES interfaces with the CIC chip?

right now, i'm just doing it the boring way. i power the fpga board externally and boot it before the snes. I think i've worked out a better way to do this by basically hardcoding a jump instruction behind a buffer that I can disable once the fpga comes up, but I haven't bothered trying it yet.

That's what I had in mind too, but I wasn't sure if I should bother with that approach or not because I'm not sure if the SNES can supply enough power to the PCB to run the FPGA and other circuitry. Do you know how much current the SNES is capable of supplying to the PCB? I think I read somewhere that even super FX carts came close to the limit.

Will you open source your board designs? I recently added my company's (Rampage Robotics) base robot board designs to my svn repo. http://svn.rampagerobotics.com/I would like to help develop.Maybe we can figure out an fpga cart for gameboy.

i don't really have any good board designs yet. things have been sort of crazy with my cross country move and getting settled into my new job, so i haven't done much work on this in awhile. but... the board isn't really that interesting anyway. all the snes io/addr pins go to the gpio pins on the fpga.

i think an gameboy cart would work pretty similar. you may want to just do a simpler cpld since i don't think gameboy has more than one memory map?